The invention relates to a device and a method for foaming a viscous material according to the teachings of the independent claims.
The generically produced foams are used, for example, though by no means exclusively, to apply foamed seals on components to be sealed in freely configurable shapes. Firstly, so-called two-component foams are known for this purpose, in which two components that are chemically reactive with each other are mixed together and yield a foam due to the chemical reaction. A disadvantage of these two-component sealing systems is that the chemical reaction can only be interrupted with great difficulty during process interruptions. For this reason, it is generally required to clean the respective device extensively following process interruptions when using such two-component systems.
In order to avoid these disadvantages of two-component systems, so-called single-component systems are known for foaming viscous materials. EP 0 286 015 B1 describes such a generic method for a single-component system. The basis of this method is the mixing of a viscous material with highly pressurized gas. After the gas has been added to the viscous material, the mixture is thoroughly mixed in a mixing device in order to ensure a sufficiently fine distribution of the gas in the viscous material. Subsequently, the mixture is discharged under high pressure and relieved of pressure upon being discharged. Via the pressure relief, it is achieved that the gas bubbles distributed in the viscous material expand due to the difference in pressure after the pressure has been relieved and consequently physically foam the viscous material. A disadvantage of this method is that the size and the distribution of the gas bubbles in the viscous material correspond to a statistical distribution so that the viscous material can also comprise relatively large gas bubbles besides minuscule gas bubbles, which can lead to irregularities when producing the foam. Due to the statistical distribution of the gas bubbles in terms of quality and quantity, a reliable process control is complicated when producing the desired foam.